The sense of hearing in human beings involves the use of hair cells in the cochlea that convert or transduce audio signals into auditory nerve impulses. Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded. These sound pathways may be impeded, for example, by damage to the auditory ossicles. Conductive hearing loss may often be helped by the use of conventional hearing aids that amplify sound so that audio signals reach the cochlea and the hair cells. Some types of conductive hearing loss may also be treated by surgical procedures.
Sensorineural hearing loss, on the other hand, is caused by the absence or destruction of the hair cells in the cochlea which are needed to transduce acoustic signals into auditory nerve impulses. People who suffer from sensorineural hearing loss may be unable to derive significant benefit from conventional hearing aid systems, no matter how loud the acoustic stimulus is. This is because the mechanism for transducing sound energy into auditory nerve impulses has been damaged. Thus, in the absence of properly functioning hair cells, auditory nerve impulses cannot be generated directly from sounds.
To overcome sensorineural hearing loss, numerous auditory prosthesis systems (e.g., cochlear implant systems) have been developed. Auditory prosthesis systems bypass the hair cells in the cochlea by presenting electrical stimulation directly to stimulation sites (e.g., auditory nerve fibers) by way of one or more channels formed by an array of electrodes implanted in an auditory prosthesis patient. Direct stimulation of the stimulation sites leads to the perception of sound in the brain and at least partial restoration of hearing function.
When an auditory prosthesis (e.g., a cochlear implant) is initially implanted in a patient, and during follow-up tests and checkups thereafter, it is usually necessary to fit the auditory prosthesis system to the patient. Fitting of an auditory prosthesis system to a patient is not an exact science but an ongoing trial-and-error-based iterative exercise that is largely dependent on the experience of and feedback provided by the patient. For example, in a fitting session, an audiologist or the like typically adjusts the value of a particular fitting parameter and relies on subjective feedback from the patient as to the effect of the adjustment. This iterative process may continue for some time until the audiologist converges on an optimal value for the fitting parameter. Unfortunately, the audiologist typically has to adjust a multitude of fitting parameters in this manner, thus causing the fitting session to be both labor and time intensive.